The intestinal microbiota is necessary to ensure optimum postnatal growth and contributes to determining the size of adult individuals, notably in the event of undernutrition. The key element in this relationship is Insulin-like Growth Factor-1 (IGF-1), whose production and activity are in part controlled by the microbiota. This has recently been demonstrated in mice by scientists at the Institut de Génomique Fonctionnelle de Lyon (CNRS/ENS Lyon/Université Claude Bernard Lyon 1), the Laboratoire CarMeN (INSERM/INRA/Université Claude Bernard Lyon 1/Insa Lyon), and Unit BF2I (INRA/INSA Lyon). These findings, published on 19 February 2016 in Science, and obtained in collaboration with researchers from the Czech Academy of Sciences, also show that some strains of intestinal bacteria belonging to the Lactobacillus plantarum species may favor the postnatal growth of animals, thus offering a new opportunity to combat the harmful effects of chronic infantile undernutrition.
During the juvenile phase, animal growth is influenced by interactions between nutritional intake and hormone signaling. Acute undernutrition for a few days in the mouse results in marked weight loss, which has been widely documented and attributed – among other factors – to a disturbance of the intestinal microbiota. Chronic undernutrition will result in the onset of growth retardation. The complex mechanisms underlying this retardation involve a state of resistance to the action of growth hormone secreted by the pituitary, an endocrine gland situated beneath the brain, which normally stimulates the production by numerous tissues of growth factors such as Insulin-like Growth Factor 1 (IGF-1). This tissue resistance to growth hormone causes a drop in the production of IGF-1, leading to a delayed development and reduced size of an individual compared with age. Until now, the influence of the microbiota on these mechanisms remained unknown.
In the mouse, the intestinal microbiota is necessary for optimum postnatal growth and thus contributes to determining the size of adult individuals. Left: an infant mouse reared with its intestinal microbiota; right: a young adult mouse devoid of intestinal microbiota. Note their difference in size. The bacterial colonization of the mice is illustrated by the presence or absence of colonies in bacterial cultures on agar plates
Image Copyright: Vincent Moncorgé